The present invention relates to spray tip assemblies for airless spray paint equipment, and in particular to a spray tip assembly that is reversible for cleaning.
Airless spray guns are employed to spray paints and other fluidic materials in a precise spray pattern. Material is supplied to the gun under very high pressure, and when the gun is triggered on the material is hydraulically forced through a small orifice in a spray tip that is typically formed of a wear resistant material such as tungsten carbide. The orifice is specially formed and usually elliptical in shape, such that emitted material is hydraulically atomized into a fan-shaped spray.
A difficulty encountered with airless spray guns is that solids in the liquid are forced into the orifice of the spray tip and trapped therein, clogging the orifice. If the spray tip is reversed on the gun, the high pressure liquid can be used to blow the obstruction from the orifice, and a number of devices have been designed to facilitate reversal of the spray tip for this purpose. One such device is a turret nozzle unit described in U.S. Pat. No. 3,116,882, in which the spray tip is mounted in a spherical housing between compressed seals to permit its rotation for reversal. Another design is shown in U.S. Pat. No. 3,563,463, in which the spray tip is carried in a housing secured to an adapter on the end of a spray gun by a collar having a transverse slot to permit the spray tip to be removed and reversed in position. In U.S. Pat. No. 3,460,757, a spray tip is carried in a housing having an externally threaded forward portion, and a separate adapter can be turned onto the threaded portion to couple the spray tip assembly to the gun in its reverse direction. A further solution is shown in U.S. Pat. No. 4,074,857, wherein a spray tip assembly is reversible within a cylindrical barrel housing which mounts it on a forward end of a spray gun.
A difficulty encountered with prior designs which permit reversing the spray tip on the spray gun is that the devices require a substantial number of parts, resulting in a greater initial cost and maintenance requirement. Additionally, many require substantial manipulation and disassembly both in reversing the spray tip and then returning it to its forward position, and often the hydraulic forces directed against the spray tip when it is reversed cause destruction of the same.